Significant Accounting Policies, Convertible Debt and Segment Information (Details)	3 Months Ended
	Mar. 31, 2015 Segment	Dec. 31, 2014	Mar. 31, 2014
Segment Information [Abstract]
Number of operating segments	2
1 Percent Convertible Senior Notes [Member]
Convertible Debt [Abstract]
Interest rate on convertible debt (in hundredths)	1.00%	1.00%
2 3/4 Percent Convertible Senior Notes [Member]
Convertible Debt [Abstract]
Interest rate on convertible debt (in hundredths)	2.75%	2.75%	2.75%